This invention generally relates to remote communication terminals for remotely controlling loads and for remotely reading meters of electric utility customers, and more particularly, to an address recognition arrangement for such terminals in which different address code formats are receivable by a discrete terminal, either singly or also simultaneously with either of two different groups of terminals, each including the discrete terminal.
To increase the efficiency and lower the cost of supplying and distributing electric energy to thousands of individual customers of an electric utility company, the requirement exists to provide reliable and low cost communication links between a central station and each of the remote customer locations. Such communication links afford control of customer loads to avoid emergency outages and to effect load shedding during peak power usage. The communication links further afford monitoring of an individual customer's power consumption on a daily or different times of day basis. Since large numbers of remote communication terminals are required for connection at each customer location, the remote communication terminal must be manufactured without excessive cost and also provide for simple and flexible communication signaling techniques for transmitting different types of command, interrogation and response data between the central station and the remote terminals. An important aspect in the design of the remote terminals is the provision of address recognition circuit configurations which will simply and efficiently authenticate different addressing formats corresponding to different types of addressing objectives to be accomplished by various data transmitted to one or more customer locations. The data transmissions may be desired to be sent exclusively to an individual terminal or simultaneously to one or more large groups of such terminals including the individual terminal. In addition to the addressing circuits, the remote terminals must incorporate therewith function control circuits to respond to selective load control commands and load status and meter reading interrogation requests.
In U.S. Pat. No. 3,702,460, a communication system for electric power utility is disclosed including a data receiving serial-input and parallel-output shift register connected to an address comparator module. The comparator module includes a diode code board and logic gates produce an output only if the remote terminal is properly addressed. Diodes are connected to the code board and to selected outputs of the shift register so as to provide a coded circuit arrangement that corresponds to an address portion of a coded data word. The aforementioned patent does not provide for a plurality of address formats or for address comparison and recognition as included in the present invention.
A utility meter remote reading system is described in U.S. Pat. No. 3,656,112 including a magnetic core memory for storing address words at a remote terminal. The magnetically stored address word bits are compared with transmitted address word bits in a parallel fashion at a shift register. Each received data bit of an interrogation message is compared with the corresponding bit of the address word in the shift register and logic circuits indicate if the received address is correct. The stored address of the remote terminal is provided by magnetic storage rather than by a fixed changeable circuit configuration as disclosed in the present invention and it does not provide for circuit changes to produce different address formats.
In U.S. Pat. No. 3,693,155 a power line communication system is disclosed having various levels of intermediate control stations or repeaters located between a base message station and a terminal control station. An interrogation receiver includes an authenticating circuit for comparison of a discrete address which is stored in a storage register. The incoming interrogation message includes address bits which are serially applied to a shift register and the contents of the shift register are transferred to a comparator which compares the contents of the discrete address register indicating that the address signals are identical. The authenticating circuit contains a number of address registers equal to the number of station levels to which the existing station is to transmit to. These registers store the addresses of all the message control stations through which the data must flow from a message station or intermediate control station to the terminal station. These multiple addresses are stored at a control station for repeating or retransmission purposes and not for addressing a given station or terminal with different address formats as included in the present invention.
In U.S. Pat. No. 3,582,922 a remote meter reading apparatus is disclosed having an address or identification coding circuit for identifying the meter which is to be read. A series of contacts are connected to either a low frequency or a high frequency tone oscillator so that as the contacts are scanned by a rotary wiper, an address signal is generated with coded high and low frequency tones. The address code generating technique is for transmission or recording of the address and not for authenticating or comparison of address at a receiving remote terminal.